Adducts of amines and polycarboxylic acids, and filter media comprising such adducts

ABSTRACT

Herein are disclosed adducts of amines and polycarboxylic acids, and methods of making such adducts. Such adducts can be used to remove cyanogen chloride. Also disclosed are methods of providing such adducts on supports to form filter media. Also disclosed are methods of combining such filter media with catalysts and/or with porous polymeric webs to form filter systems.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/388,647, filed Feb. 19, 2009, which Application claimed the benefitof U.S. Provisional Patent Application No. 61/030,304, filed Feb. 21,2008, the disclosures of both of which are incorporated by referenceherein in their entirety.

BACKGROUND

Cyanogen chloride is an extremely toxic gas, so its removal fromrespirable air is highly desirable. Certain amities, for example,triethylenediamine, have been found to be capable of removing cyanogenchloride, and are often used in combination with (e.g., incorporated on)sorbent materials such as activated carbon, in applications such asrespiratory protection.

Carbon monoxide is also toxic, so its removal from respirable airstreamsis also highly desirable. Various materials and substances (e.g. thewell-known Hopcalite catalyst, and certain metal catalysts, for example,gold), have been found to be capable of catalyzing the oxidation ofcarbon monoxide to carbon dioxide and have been proposed for variousrespiratory protection applications.

SUMMARY

Herein is disclosed an amine adduct and a method of making such anadduct. In one embodiment, the adduct is formed by combiningtriethylenediamine (henceforth abbreviated as TEDA) with apolycarboxylic acid. The inventors have found the surprising result thatforming TEDA into such an adduct lowers the volatility of TEDA, thusreducing many of the undesirable side effects of TEDA (for example itsodor, its tendency to irritate eyes and skin, its tendency to poison orreduce the effectiveness of certain catalysts, its tendency to reducethe effectiveness of certain filtration media, particularly so-calledelectret filter media, etc.), while preserving or even enhancing theability of the TEDA to remove cyanogen chloride.

Also disclosed are methods of combining TEDA and polycarboxylic acids soas to form such adducts. Additionally disclosed are adduct compositionswhich have been found to be particularly usefule. Further disclosed isthe incorporation of adducts onto supports (e.g., high or extendedsurface area materials such as activated carbon and certain aluminas),so as to form filter media. Such filter media can be usefully employedin various types of respiratory protection products and systems.

Additionally disclosed are filter systems comprising adducts asdescribed herein (in particular, adducts provided on supports) that areuseful in the removal of, e.g., cyanogen chloride, in combination withcatalysts that are useful in the removal of other materials, e.g.,carbon monoxide. The inventors have found the surprising result thatsuch adducts and such catalysts can be employed in the same filtersystem, without either one unacceptably reducing the performance of theother. In a particular embodiment, such catalysts comprise gold clustersof size about 0.5 tun to about 50 nm, which can be used to catalyze theoxidation of carbon monoxide to carbon dioxide. Such gold catalysts areknown to be susceptible to poisoning (e,g., are known to have theircatalytic activity inhibited) by amines. The inventors have found thesurprising result that such gold catalysts and TEDA can be used in thesame filter system, if the TEDA is present in the form of an adduct witha polycarboxylic acid.

Additionally disclosed are filter systems comprising adducts asdescribed herein (in particular, adducts provided on supports) that areuseful in the removal of e.g., cyanogen chloride, in combination withfilter media that are useful in the removal of particulates. Inparticular, such adducts are useful in combination with porous polymericfiltration media of the type generally referred to as electret webs. Theinventors have found the surprisingly result that such adducts andelectret webs can be employed in the same filter system, without eitherone unacceptably reducing the performance of the other.

Filter media containing TEDA/polycarboxylic acid adducts, filter systemscontaining such adducts in combination with gold catalysts, and/orfilter systems containing such adducts in combination with electretwebs, can be included in respiratory protection devices, as described indetail herein. Such respiratory protection devices can include devicesfor personal protection (that is, protection of a single individual), orfor so-called collective protection (that is, devices that protect ortreat the air to which mutt pie individuals are exposed). Suchcollective protection devices may be used in, e.g., vehicles, buildings,work environments (mines, factories, etc.), and the like.

Thus disclosed herein in one aspect is a filter medium, comprising asupport and an adduct of triethylenediamine and a polycarboxylic acidprovided on the support.

Disclosed herein in another aspect is a method of making a filtermedium, comprising the steps of providing triethylenediamine and atleast one polycarboxylic acid; combining the triethylenediamine with thepolycarboxylic acid under conditions effective to form an adductthereof; and, causing the adduct to be provided on a support.

Disclosed herein in another aspect is a method of removing cyanogenchloride from a gaseous stream, comprising the steps of providing afilter medium comprising a support with an adduct of triethylenediamineand a polycarboxylic acid provided on the support; and, exposing thegaseous stream to the filter medium.

Disclosed herein in yet another aspect is a filter system, comprising: afilter medium comprising a support comprising an adduct oftriethylenediamine and a polycarboxylic acid; and, a catalyst active forthe oxidation of carbon monoxide.

Disclosed herein in yet another aspect is a filter system, comprising: afilter medium comprising a support comprising an adduct oftriethylenediamine and a polycarboxylic acid; and, a filter mediumcomprising a porous polymeric web.

Disclosed herein in still another aspect is an adduct oftriethylenediamine and a polycarboxylic acid, wherein the adduct isselected from the group consisting of: a 1:1 stoichiometric adduct oftriethylenediamine and succinic acid, wherein the adduct exhibits anX-ray diffraction pattern of 4.4 (100), 2.4 (14), 3.1 (12), and 4.1 Å(11); a 1:1 stoichiometric adduct of triethylenediamine and succinicacid, wherein the adduct exhibits an X-ray diffraction pattern of 3.9(100), 5.0 (89), 4.3 (62), 5.6 (55), and 3.8 Å (51); a 1:1stoichiometric adduct of triethylenediamine and malic acid, wherein theadduct exhibits an X-ray diffraction pattern of 6.2 (31), 5.5 (44), 4.8(36), 4.6 (57), 3.9 (55), and 3.4 Å (100); a 1:1 stoichiometric adductof triethylenediamine and tartaric acid; a 1:1 stoichiometric adduct oftriethylenediamine and malonic acid; a 1:1 stoichiometric adduct oftriethylenediamine and citric acid; and, a 1:1 stoichiometric adduct oftriethylenediamine and glutamic acid.

DRAWINGS

FIG. 1 is a schematic view in cross-section, of an exemplary filtersystem.

FIG. 2 is a perspective view of an exemplary respiratory device forpersonal protection.

FIG. 3 is a schematic view in cross section, of another exemplary filtersystem.

Drawings and elements therein are not to scale unless noted. In theFigures, like reference numerals are used to designate like featuresthroughout. Although terms such as “top”, bottom”, “upper”, lower”,“over”, “under”, “front”, “back”, and “first” and “second” may be usedin this disclosure, it should be understood that those terms are used intheir relative sense only.

DETAILED DESCRIPTION

Disclosed herein are adducts formed by combining an amine and apolycarboxylic acid. In various embodiments, the amine may he primary,secondary, or tertiary, and may be solid or liquid at room temperature(i.e., about 25° C.), at 1 attn. Preferred amines possess at least someability to remove toxic gases such as cyanogen chloride and the like. Invarious embodiments, suitable amines may include triethylamine (TEA) orquinuclidine (QUIN); trieklenediamine (TEDA); pyridine, pyridinecarboxylic acids such as pyridine-4-carboxylic acid (P4CA), combinationsof these, and the like. In a presently preferred embodiment, the amineis triethylenediamine (commonly abbreviated as TEDA), also known as1,4-diazabicyclo[2.2.2]octane (commonly abbreviated as DABCO).

The term polycarboxylic acid as used herein means an organic moleculethat contains at least two carboxylic acid groups. Such molecules may bewritten in general form as R(COOH)_(x), where x is equal to or greaterthan 2, and where R can comprise a covalent bond (in the case of oxalicacid) or a hydrocarbon moiety (e.g., an alkyl, aromatic, alkenyl, etc.,group). In one embodiment, the polycarboxylic acid comprises twocarboxylic acid (COOH) groups. Thus, suitable polycarboxylic acids mayinclude e.g. oxalic acid, malonic acid, succinic acid, glutaric acid,adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalicacid, and combinations thereof. In another embodiment, thepolycarboxylic acid comprises three carboxylic acid groups. Suitablecarboxylic acids of this type include e.g. citric acid. In still anotherembodiment, the polycarboxylic acid comprises four or more carboxylicacid groups. In a particular embodiment, the polycarboxylic acid ispolymeric in nature. For example, the polycarboxylic acid can comprise arelatively long chain backbone with pendant carboxylic acid groups, asexemplified by poly(acrylic acid).

In a one embodiment, the polycarboxylic acid contains at least onehydroxyl group that is not part of a carboxylic acid group (that is, inaddition to the hydroxyls present on the carboxylic acid groups). Suchhydroxy polycarboxylic acids are of particular interest because of theirmoderate acidity and low toxicity, and can include polycarboxylic acidswith two, three, or four or more carboxylic acid groups. For example,suitable hydroxy carboxylic acids may include e,g, malic acid, citricacid, and tartaric acid.

In various embodiments, the polycarboxylic acid can comprise othersubstituents or groups in addition to hydrocarbon moities and theabove-mentioned optional hydroxyl group(s). For example, the R group cancomprise any suitable component or substituent (e.g. NH₂, as in the caseof glutamic acid; HS, as in the case of thiomalic acid, etc.).

While not being limited by theory or mechanism, it is postulated thatthe Bronsted acidic nature of such polycarboxylic acids (i.e. theirpossession of one or more donatable protons) may be at least partlyresponsible for their ability to form suitable adducts with TEDA. Inparticular, their somewhat acidic (i.e., weakly acidic) nature mayfacilitate sufficient acid/base interaction between the polycarboxylicacid and the TEDA to form an adduct, without however being so acidic asto completely protonate the TEDA to form a salt, which might bedisadvantageous. (For example, the inventors found that reaction of TEDAwith HCL resulted in the formation of an onium salt (his hydrochloride)of TEDA, which did not function well in removing cyanogen chloride). Itis thus noted that although the polycarboxylic acids advantageouslycontain acidic, ionizable or donatable protons, complete proton transfer(i.e., salt formation) may not occur in the formation of the adducts.

A single polycarboxylic acid may be used, or multiple polycarboxylicacids (e.g., any of the above-mentioned polycarboxylic acids) may beused in combination. Other compounds, materials, etc. may be present forvarious purposes as long as they do not unacceptably reduce the abilityof the polycarboxylic acid and TEDA to form an adduct, or unacceptablyreduce the ability of the adduct to perform the functions describedherein.

In one embodiment, the polycarboxylic acid is water soluble, which canrender the adduct amenable to being produced by solution-based (e.g.water-based) methods as described later herein. In a specificembodiment, the polycarboxylic acid is water soluble to sufficientextent that when dissolved in water at a level of 0.2% by weight at 25°C., it forms a clear, isotropic liquid.

In one embodiment, the polycarboxylic acid is of relatively lowmolecular weight (e.g., less than 150 grams/mole, as exemplified by manyof the acids listed above). In other embodiments, the polycarboxylicacid may comprise a higher molecular weight (e.g. greater than 150grams/mole, greater than 200 grams/mole, or greater than 300grams/mole). In further embodiments, the polycarboxylic acid maycomprise a molecular weight of less than about 1000 grams/mole, lessthan 500 grams/mole, or less than about 300 grams/mole. Theabove-mentioned polymeric polycarboxylic acids may have relatively highmolecular weight, e.g. greater than 1000 grams/mole. If it is desiredthat the polycarboxylic acid be water soluble (e.g., to aid insolution-based processing), the molecular weight of the polymericpolycarboxylic acid can be selected for optimum water solubility.

The herein-disclosed adducts of TEDA and various polycarboxylic acidscan also be described as complexes, and are reproducibly manufacturableaccording to methods taught by herein, and exhibit reproducibleproperties as disclosed herein. The inventors have found such adducts tobe useful in reducing the disadvantages and side effects of TEDA, whilepreserving and potentially even enhancing the ability of the TEDA toremove cyanogen chloride.

In particular, forming TEDA into an adduct can serve to reduce thevolatility of TEDA in comparison to that of free (uncomplexed) TEDA. Dueto the properties of TEDA (odor, ability to irritate skin and eyes,ability to poison certain catalysts, ability to cause discoloration ofcertain polymeric materials, etc.), such a reduction in volatility isquite useful.

The inventors have also found that the adducts described herein cancomprise unexpectedly high thermal stability. For example, some adductshave been observed to survive extended periods of exposure to elevatedtemperature (for example, being dried under vacuum at 60° C.) withoutsignificant weight loss. Thermogravimetric testing (e.g., determinationof the amount and/or rate of weight loss that occurs on heating tovarious temperatures) has revealed some adducts to exhibit umimodalweight loss-versus-temperature curves. This indicates that upon heating,a TEDA-containing adduct may be volatilized, at elevated temperatures,rather than the adduct dissociating to release/volatilize (free) TEDA atlower temperatures. Such a result may be unexpected in view of the factthat many such amine-containing materials (e.g. onium salts, such asammonium chloride) are commonly known to dissociate on heating such thatthe constituents are volatilized separately.

Thermogravimetric testing has also revealed (see Table 1 of the Examplessection) that some adducts comprise a T_(max) (temperature of maximumrate of weight loss upon heating) that is near, and in some cases evenhigher than, the relatively higher T_(max) of the polycarboxylic acidconstituent, rather than being near the relatively lower (expected)T_(max) of the TEDA constituent (TEDA being so volatile that a T_(max)would be difficult to measure). Such a finding (T_(max) of the adductbeing near to or higher than that of the highest-T_(max) parentconstituent) is unexpected.

In addition, the inventors have discovered that TEDA in the form of theherein-described adducts can comprise preserved or even enhanced abilityto remove cyanogen chloride. (For example, it has been found thatcertain TEDA/adducts can exhibit a longer CK Service Life, as describedherein, than exhibited by TEDA when not in the form of an adduct). Thesurprising discovery has been made that TEDA can be formed into anadduct in which the volatility is reduced, but in which the TEDA isstill accessible by the cyanogen chloride, able to interact with thecyanogen chloride, and able to remove the cyanogen chloride, e.g., froma gaseous stream.

Adducts of TEDA with various polycarboxylic acids are disclosed herein.In a particular embodiment, the adduct comprises about a 1:1stoichiometric ratio between the TEDA molecules and the polycarboxylicacid molecules. (Such a stoichiometric ratio, however, does not implythat any sort of specific chemical reaction, so as to form a specificchemical bond, occurs in the formation of the adduct).

At least some of the adducts disclosed herein appear to be polymorphs(polymorphism being defined herein as the property of some molecularcomplexes to assume more than one form, e.g. more than one crystallineform, in the solid state). The structure of such polymorphs can besensitive to the method of production and different polymorphs from thesame parent constituents can have distinctly different properties. Suchpolymorphs are often characterized by methods such as X-Ray Diffraction,Infrared Absorption, Differential Scanning calorimetry, and the like.For example, different polymorphs typically exhibit diffraction patterns(i.e., different sets of peaks (intensities) found at differenttwo-theta (scattering) angles.

Adducts as disclosed herein may comprise one or more water molecules(e.g., waters of hydration). The presence or absence of water in theadduct may be dependent on the method of preparation. Thus in some casesthe adduct may comprise one or more waters of hydration as prepared.(For example, with reference to the TEDA-succinic acid adduct of Example2 discussed later herein, the Infrared Spectroscopy peaks at 3561 cm-1and 3476 cm-1 appear to be ν_(OH) bands and the peak at 1642 cm-1appears to be a δ_(OH) band, all of which are indicative of water ofhydration). Even if prepared so as to be initially lacking water, insome cases adducts may acquire water during storage and/or use (e.g.,the adduct may acquire water upon exposure to humid air). For example,some adducts appear to be able to reversibly acquire water (e.g., whenexposed to water-saturated air or nitrogen). In some cases mixtures ofhydrated and anhydrous adducts may be found.

Under suitably controlled conditions, TEDA and a suitable polycarboxylicacid can be brought together so as to combine to form an adduct. Thisdoes not necessarily imply the formation of a defined chemical bond(e.g., a covalent bond, an ionic bond, etc.) between the TEDA and theacid. Nor does it necessarily imply the formation of a product with aspecific molecular structure. Rather, as discussed above, the adductproduct of combining the TEDA and the polycarboxylic acid may bedescribed as a complex or polymorph.

Various methods of making such adducts are disclosed herein. Suchmethods include any procedure in which TEDA and one or morepolycarboxylic acids are brought together and combined to form anadduct. For example, TEDA may be deposited onto a support, after which apolycarboxylic acid is deposited onto a support under conditions suchthat an adduct can form. Or, the polycarboxylic acid may be firstdeposited, after which TEDA is deposited under conditions such that anadduct can form. Such deposition may occur by any known methodincluding, e.g., vapor deposition, sublimation, impregnation, etc., aslong as conditions are controlled such that adduct formation occurs.

In various embodiments, processes can be used in which the TEDA and theacid are brought into contact under conditions optimum for the formationof such adducts. For example, the TEDA can be provided in an environmentin which there are little or no other entities (e.g. molecules, atoms,colloids, micelles, etc.) present that can react with the TEDA, form acomplex with it, cluster around it, or otherwise chemically interactwith, or physically block, the TEDA in such a manner as to prevent itfrom combining with the acid to form the adduct. In particular, it maybe advantageous to provide the TEDA in a maximally accessible condition(for example, not condensed on a solid material such as a support) inorder to form the adduct. Likewise it may be advantageous to provide thepolycarboxylic acid in a similarly accessible condition. Thus, in oneembodiment a method of combining TEDA and a polycarboxylic acid isdisclosed in which the TEDA and the acid are physically mixed and groundtogether.

An alternative embodiment comprises a method in which the TEDA and thepolycarboxylic acid are placed (e.g. suspended, dissolved, etc.) into acommon mixture (e.g., a solution in a suitable solvent or solventmixture, such as water, alcohol, a water-alcohol mixture, etc.) afterwhich a portion or essentially all of the solvent is removed. Theinventors have found such a process to be particularly useful information of adducts. In various embodiments the TEDA and thepolycarboxylic acid may form an adduct in the initial solution (whichadduct is recovered upon solvent removal, filtration, etc.); or, theTEDA and the polycarboxylic acid may form an adduct during the late orfinal stages of solvent removal, e.g. concurrently with a drying,precipitation, and/or crystallization process. Also, in variousembodiments the TED and/or the polycarboxylic acid may be solubilized inthe common mixture so as to Dorm a stable solution; or, one or the othermay be present in the form of a metastable solution; or, one or theother may be present in the form of a suspension. (In some cases onecomponent may comprise a suspension prior to the addition of the othercomponent, which addition may result in the first component being betterable to be solubilized such that a solution is formed). Any suchcircumstance is encompassed within the methods disclosed herein, as longas a suitable adduct product can be reproducibly obtained from theprocess.

In various embodiments, herein are disclosed methods of making adductsin which the TEDA and the polycarboxylic acid are brought together inamounts that are in the range suited to form 1:1 adducts (for example,bringing TEDA and an acid together in a stoichiometric (molecular) ratioranging from about 1.1:1 TEDA/acid to about 1.1:1 acid/TEDA). In aparticular embodiment, a slight excess of acid can be used in order toprovide that little or no free TEDA (that is, TEDA that is not in theform of an adduct with the acid) is present after the materials arecombined. Such an arrangement can minimize the adverse effects(volatility, etc.) of free TEDA as mentioned previously. In anadditional embodiment, the production process can include the removal offree TEDA after the materials are combined. Such a process can includefor example heating, which can be performed either before or after theadduct is deposited onto a support.

In the case of a polymeric (e.g., high molecular weight) polycarboxylicacid, a 1:1 molecular ratio of the acid molecule(s) and the TEDAmolecule(s) may not exist in the manner that would be obtained whenusing a small-molecule polycarboxylic acid. That is, carboxylic acidgroups on various portions of the polymer backbone may interact withdifferent TEDA molecules, thus a 1:1 ratio of TEDA molecules topolycarboxylic acid molecules may not be present. In such a case, theadduct may not comprise 1:1 stoichiometric adduct. Nevertheless, such aTEDA/polymeric polycarboxylic acid combination product is within thescope of the concept of an adduct as contemplated by the inventors.

In one embodiment, TEDA and a polycarboxylic acid are provided on asupport so as to form a filter medium (e.g., an air-permeable structure,assembly, matrix, collection of particles, etc., that is designed toremove contaminants from air that passes through it).

The support may be selected from a wide variety of substrates. Thesupport may have a convoluted, textured and/or porous surface and invarious embodiments is capable of being incorporated with at least about0.1%, at least about 1.5%, or at least about 3%, by weight of one ormore impregnants including the adduct.

The support may have many forms. Representative examples of such formsinclude woven or nonwoven fabric; bonded, fused, or sintered block;particles, granules, or pellets; filtration media arrays, etc. In oneembodiment, the support comprises particles with a relatively highsurface area. In various embodiments, such particles comprise a (BET)specific surface area (as can be determined by the procedure describedin ISO 9277:1995) of at least about 85 m²/g, at least about 300 m²/g, orat least about 900 m²/g. In additional embodiments, such particles haveBET specific surface areas of at most about 2000 m²/g, or at most about1500 m²/g.

The support may comprise porosity. In one embodiment, the supportcomprises a porosity (that is, the volume ratio of pore space to thetotal volume of the support medium) greater than about 0.4. Suchporosities can he observed and measured, for example via transmissionelectron microscopy (TEM).

In a specific embodiment, the support comprises nanoporosity (that is,it comprises a porosity greater than about 0.4 and an average porediameter, as characterized by TEM, ranging from about 1 nm to about 100nm in size).

In a particular embodiment, the support media comprises a totalNanoporous Capacity for pores in the size range of 1 to 10 nm that isgreater than about 20 percent (that is, greater than about 0.20 usingthe formula below) of its total volume of pores in the size range of 1to 100 nm, as calculated using the following formula:

${NPC} = \frac{{CPv}_{1} - {CPv}_{10}}{{CPv}_{1} - {CPv}_{100}}$

wherein NPC refers to the Nanoporous Capacity of the support medium;CPv_(n) refers to the cumulative pore volume at pore radius n in cubiccentimeters per gram (cm³/g); and n is the pore radius in nanometers.

In a specific embodiment, the Nanoporous Capacity is calculated usingdata obtained by TEM. In an alternative embodiment, the data used isobtained by use of nitrogen desorption isotherms according to thetechnique described in ASTM Standard Practice D4641-94.

The support may be made of various materials. Representative examples ofsuch materials include paper, wood, polymers and other syntheticmaterials, carbonaceous materials, silicaceous materials (such assilica), metals, metal compounds, and combinations thereof.Representative examples of suitable metal compounds include oxides,sulfides, nitrides, or like compounds of magnesium, aluminum, titanium,vanadium, chromium, manganese, cobalt, nickel, copper, zinc, gallium,germanium, strontium, yttrium, zirconium, niobium, molybdenum,ruthenium, rhodium, palladium, silver, cadmium, indium, iron, tin,antimony, barium, lanthanum, hafnium, tungsten, rhenium, osmium,iridium, platinum, and combinations thereof. Representative examples ofsuitable carbonaceous materials include activated carbon and graphite.Suitable activated carbon may be derived from a wide variety of sourcesincluding coal, coconut, peat, and combinations thereof.

In one embodiment, the activated carbon comprises that class ofmaterials known as whetlerites, which can be generally described asactivated carbons that contain certain metals, or oxides of metals, suchas copper, molybdenum, silver, vanadium, zinc, and so on. In a furtherembodiment, the activated carbon comprises those materials generallydescribed in U.S. Pat. No. 5,344,626, herein incorporated by referencein its entirety. In a particular embodiment, the activated carboncomprises a first metal salt wherein the metal is in group 6-12 of theperiodic table; and, a second metal salt that comprises a metalcarbonate salt, wherein the metal is in group 1 of the periodic table.

In a particular embodiment the support comprises a guest/host structure.Such a support can be made by providing (e.g., depositing, adsorbing,growing, or adhering) relatively smaller guest particles on relativelylarger host particles (such as larger particles, powders, pellets,granules, and combinations thereof), or on relatively largernonparticulate host material (such as woven and nonwoven media,membranes, plates, filtration media arrays, and combinations thereof).Such a guest/host structure can provide higher total exterior surfacearea while retaining the desirable gas flow characteristics, e.g., lowpressure drop, of a larger particle, in such a case, the adduct can bepositioned on the guest, the host, or both.

Either the guest and/or the host can comprise porosity or nanoporosity,as herein defined. The guest and the host can be made of various supportmaterials as described herein. In a specific embodiment, the guestmaterial comprises titania, and the host material comprises activatedcarbon.

A variety of methods generally may be used to construct a guest/hostsupport. In one embodiment, smaller guest particles are admixed with oneor more adhesion agents in solution and then this mixture is combinedwith larger host particles. In another embodiment, guest-host compositesare prepared by physically mixing guest and host materials.

In one embodiment, an adduct is formed after which the formed adduct isincorporated onto/into a support (with certain supports, e.g. porousmaterials, such an into/onto distinction may be difficult tocharacterize; either term is intended to broadly encompass any processin which an adduct is placed in contact with the interior and/orexterior surface of a support). For example, adduct pre-formed by thepreviously-described mixing/grinding process can be deposited onto asupport. In another embodiment, the adduct is formed in situ on thesupport. For example, TEDA can be incorporated (e.g. deposited,impregnated, condensed, etc.) onto a support after which polycarboxylicacid is added to form the adduct. Or, polycarboxylic acid can beincorporated onto the support after which TEDA is added to form theadduct.

In another embodiment, a mixture (e.g. a solution, a metastablesolution, a suspension, etc.), obtained for example by thepreviously-described process of dissolving the TEDA and thepolycarboxylic acid in a common solvent, is incorporated (e.g.deposited, impregnated, coated, sprinkled, misted etc.) onto a support,after which some or all of the solvent(s) is removed (e.g. evaporated).Such an embodiment may possess particular advantages in allowinglarge-scale processing in the production of filter media.

In various embodiments, appropriate amounts of TEDA and polycarboxylicacid may be chosen, and/or processing conditions may be chosen, so thatan adduct with about a 1:1 TEDA/polycarboxylic acid stoichiometric ratiois obtained. In particular, the mixing/grinding method and thecommon-solution method can allow selection of the TEDA/polycarboxylicacid stoichiometric ratio, and can allow the components to be combinedin such a way, as to promote the formation of an adduct with about a 1:1stoichiometric ratio of TEDA/polycarboxylic acid. This may beadvantageous in minimizing the need for removal of an excess of eithercomponent (particularly the TEDA, in view of the already-mentionedproblems associated with free TEDA). However, such a removal procedurecan be carried out if desired. For example, the support can be heated soas to volatilize the free TEDA.

In a particular embodiment, so-called incipient wetness impregnationmethods are used to deposit the adduct on the support. In such methods,an aqueous mixture containing the adduct or the adduct precursorconstituents (e.g., a solution, suspension, etc. of the adduct in water,or a solution, suspension, etc. of the adduct precursors, etc.) isprovided. As discussed earlier, the aqueous mixture may comprise otheringredients (e.g. a cosolvent or cosolvents of various types), asdesired. The aqueous mixture is gradually added to the support withconstant stirring. This is continued until the support appears to besaturated with the aqueous mixture. (Typically, the support is dryinitially so that the point of saturation of the support is more readilyobserved). The wetted support is then dried at a suitable temperaturefor a suitable time period. By way of example, drying the impregnatedsupport at a temperature in the range of about 50° C. to about 250° C.,preferably about 80° C. to about 180° C., for a time period in the rangeof about 30 minutes to about 10 hours, would be suitable. Theimpregnated support is then cooled. Optionally, the impregnation,drying, and cooling may be repeated one or more times to impregnateadditional amounts of the amine adduct onto and into the support. Thedrying period and temperature may be extended, if desired, to helpensure that any free TEDA (i.e., TEDA that is not part of an adduct) isdriven off. Any free TEDA that is driven off can be recovered and thenrecycled or discarded as desired.

If other materials are desired to be impregnated into/onto the supportusing impregnation techniques, the adduct may be impregnated into/ontothe support, before, during, and/or after impregnation of the otherimpregnants. In the particular embodiment in which one or more otherco-impregnants are to be impregnated into/onto the support by other,non-wet impregnation techniques such as sublimation, physical vapordeposition, chemical vapor deposition, or the like, wet impregnation ofthe adduct may occur before or after the other, non-wet impregnationstep.

The amount of adduct incorporated into/onto the support may vary over awide range. In general, if too little is used, the Cyanogen ChlorideService Life of the filter media, as measured in the test disclosedlater herein, may be shorter than desired. On the other hand, using toomuch adduct may tend to reduce the capacity of the filter media toremove other contaminants (e.g., organic vapors, acid gases, etc.). Inview of these considerations, in various embodiments the adduct can beintroduced into/onto the support at levels corresponding to at leastabout 0.1 parts by weight of TEDA, at least about 0.5 parts by weight ofTEDA, or at least about 3.0 parts by weight of TEDA, all relative to 100parts by weight of the support. In additional embodiments, the adductcan be introduced into/onto the support at levels corresponding to atmost about 25 parts by weight of TEDA, at most about 10 parts by weightof TEDA, or at most about 6 parts by weight of TEDA, all relative to 100parts by weight of the support.

Herein is also disclosed a filter system which comprises one or morecatalysts in addition to comprising a filter medium that comprises aTEDA/polycarboxylic acid adduct. In various embodiments, such catalystsmay be positioned on the same support as the TEDA/polycarboxylic acidadduct, or on a separate support. Such a separate support may beintermingled with the support comprising the TEDA/polycarboxylic acidadduct (as in the embodiment of FIG. 1, discussed later in detailherein), or may be in a separate location (e.g. In a separate layer in acartridge, in a separate cartridge, etc.) from the support comprisingthe TEDA/polycarboxylic acid adduct. For example, if the performance ofthe particular catalyst used is somehow sensitive to the presence of theTEDA/polycarboxylic acid adduct, the catalyst may be placed in thefilter system such that the catalyst is upstream from the adduct (inthis context, upstream means that in operation of the filter system, agaseous stream flowing through the filter system would encounter thecatalyst prior to encountering the TEDA/polycarboxylic acid adduct).Conversely, if the performance of the adduct is somehow sensitive to thepresence of the catalyst, the TEDA/polycarboxylic acid adduct may beplaced in the filter system upstream from the catalyst.

In various embodiments, catalysts that may be useful in such filtersystems include metal catalysts such as platinum, silver, nickel,palladium, rhodium, ruthenium, osmium, copper, iridium, and combinationsthereof In a particular embodiment, catalytically active gold (e.g.,elemental gold) is used, either alone or in combination with one or moreof the other metal catalysts listed above. In this context,catalytically active gold signifies gold of cluster size of about 0.5 nmto about 50 nm, that is active to, for example, oxidize carbon monoxideto carbon dioxide. Such gold catalysts are known to those of skill inthe art to be sensitive to amines (such as TEDA); i.e. amines are knownto tend to poison or inhibit the catalytic activity of gold in reactionssuch as CO oxidation. However, the inventors have surprisingly foundthat when the TEDA is formed into an adduct with a polycarboxylic acid,catalytically active gold appears to be less sensitive to the presenceof the amine. The inventor's discoveries thus allow the use of filtersystems that comprise the dual functionality of TEDA to remove cyanogenchloride, and catalytically active gold to oxidize CO.

Catalytically active gold can be deposited in a variety of methodsincluding so-called wet methods (including solution-deposition and thelike), and chemical vapor deposition, and can be deposited onto anysuitable substrate as desired. In various particular embodiments, thegold can be deposited by physical vapor deposition, and/or can bedeposited onto supports that have particular properties of composition,size or porosity, or that comprise guest/host structures, or thatinclude various promotor materials, or that comprise other propertiesand attributes, all as described in detail in US Patent Publication2005/0095189, which is incorporated by reference herein in its entirety.

Herein is also disclosed a filter system which comprises a porouspolymeric web based filter medium in addition to comprising a filtermedium that comprises a TEDA/polycarboxylic acid adduct. Such a porouspolymeric web, which can comprise a woven web, a nonwoven web (oftencomprised of so-called blown microfibers of a material such as apolyolefinic material), an open-cell foam material, and the like, isoften used for filtration of particulates.

In one embodiment, the porous polymeric web comprises a so-calledelectret web, i.e., a web that comprises a dielectric material thatexhibits at least a quasi-permanent electric charge. Such charged webshave been known since, for example, Kubik et al. described (in U.S. Pat.No. 4,215,682) a method for introducing a persistent electric chargeinto meltblown fibers during fiber formation. In various embodiments,such electret webs may comprise fluorinated materials, as achieved forexample by methods such as plasma fluorination (e.g., as described inU.S. Pat. No. 6,409,806), or by incorporation of fluorochemical meltadditives (e.g. as described in U.S. Pat. No. 5,025,052). In variousadditional embodiments, such webs may comprise hydrocharged materials(that is, webs in which an electric charge is imparted by exposing theweb to a stream of water) as described in U.S. Pat. No. 5,496,507.

Electret webs are known to those of skill in the art to be sensitive toamines (such as TEDA); i.e. amines are known to tend to reduce theefficiency of electret webs. However, the inventors have surprisinglyfound that when the TEDA is formed into an adduct with a polycarboxylicacid, such electret webs appear to be less sensitive to the presence ofthe amine. The inventor's discoveries thus allow the use of filtersystems that comprise the dual functionality of TEDA to remove cyanogenchloride, and electret webs that provide excellent removal ofparticulates.

A filter system may be produced containing both a TEDA/polycarboxylicacid adduct (typically on a support) and a porous polymeric web, in anynumber of ways. In one embodiment, the TEDA/polycarboxylic acid adductmay be deposited or otherwise placed or incorporated into/onto theporous polymeric web (i.e., the porous polymeric web may function as thesupport for the TEDA/polycarboxylic acid adduct, in a configurationdescribed previously herein). In another embodiment, the adduct can beprovided on a support (e.g., activated carbon), which is then deposited,embedded, intermingled, etc., into/onto the porous polymeric web. Instill another embodiment, the porous polymeric web and theTEDA/polycarboxylic acid adduct may be present at separate locations inthe filter system (e.g., as separate layers in a cartridge, in separatecartridges, etc.). For example, such porous polymeric webs are oftenpositioned in filtration systems as an upstream layer, with additionalfilter media (e.g., activated carbon) present downstream from the porouspolymeric web layer (in this context, upstream means that in operationof the filter system, a gaseous stream flowing through the filter systemwould encounter the porous polymeric web layer prior to encountering theTEDA/polycarboxylic acid adduct). Such a configuration is shown in anexemplary manner in FIG. 3, described later herein.

In summary, a porous polymeric web, present in a filter system in any ofthe above-described configurations, may comprise an electret material.The porous polymeric web may be flat, pleated, folded, supported by areinforcing structure, etc., all according to methods known in the art.Additionally, filter systems as described herein may includeTEDA/polycarboxylic acid adducts in combination with both theabove-described gold catalysts and the above-described porous polymericwebs (including electret webs).

Filter media or filter systems as disclosed herein may also comprise asuitable filtering agent. Such a filtering agent can be provided on thesupport comprising the adduct, the support comprising the catalyst (ifone is used), or elsewhere in the filter system. The term filteringagent generally refers to any ingredient that may help to filter one ormore undesired gases from an air stream. In various embodiments,suitable filtering agents include metals, metal alloys, inter metalliccompositions, compounds containing one or more of copper, zinc,molybdenum, silver, nickel, vanadium, tungsten, yttrium, cobalt, andcombinations thereof. For example, Cu may help to filter HCN, H₂S, andacid gases; Zn may help to filter HCN, cyanogen chloride, cyanogen, andNH₃; Ag may help to filter arsenical gases; and Ni and Co eachindependently may help to filter HCN.

Such filter media (which may be the filter medium that comprises theadduct, or the filter medium that comprises the catalyst) may beincorporated, with about 0.1 to about 20 weight percent of filteringagent(s) based upon the total weight of the filtering agent(s) and thefilter medium. The filtering agent(s) typically are provided as salts,oxides, carbonates, or the like and are incorporated via solutionprocessing, sublimation processing, fluidized bed processing, or thelike.

Water may or may not be a desired impregnant for any of the variousfilter media that are present in the filter system. For instance, if ametal catalyst, particularly catalytically active gold, is included,moisture can impair the activity of the catalyst upon storage for longperiods of time. Consequently, it may be desirable to minimize theamount of water that is present in the filter system if a metal catalyst(e.g., catalytically active gold) is included. Thus, in variousembodiments a filter system may comprise a filter medium that includesless than about 2 parts by weight, or less than about 1 part by weight,of water per 100 parts by weight of the filter medium.

However, moisture may beneficially help to remove acid gases from an airstream. Consequently, (particularly if metal catalysts are notincluded), in various embodiments the filter media may include at leastabout 2 parts by weight, up to about 15 parts by weight, or up to about12 parts by weight, of water per 100 parts by weight of the filtermedium.

Filter media and/or filter systems as described herein are suitable forapplication in respiratory protection to remove a broad range of toxicgases and vapors as found in industrial environments and also chemicalsused as chemical warfare agents. The filter systems may achieveperformance levels mandated both by applicable industrial filterapproval specifications and by internationally recognized militaryfilter performance specifications. In specific embodiments, the adductsand/or catalysts disclosed herein are used with activated carbonsupports, in order to improve the ability of the activated carbon toremove, e.g., low boiling point toxic gases. In specific applications,these filter media and/or filter systems are used to filter breathingair in connection with personal and/or collective (e.g., building ormotor vehicle) respiratory protective devices. Respiratory protectiondevices include devices or equipment for providing clean or cleansed airor oxygen as breathing air to a user or users. Such devices may includefor example full face respirators, half mask respirators, supplied airhoods, powered air purifying respirators (PAPRs), etc. The broadcapabilities of the filter media and/or filter systems disclosed hereinrender them suitable for a wide variety of applications, including beingfitted onto a face-mask, or being fitted singly or in multiples onto apowered air purifying respirator system. One such powered system iscommercially available under the trademark “BREATHE-EASY” from 3MCompany. However, the utility of the present invention is not limited torespiratory protective equipment, but also can be used for purifying airor other gases in connection with industrial processes.

FIGS. 1, 2, and 3 show various exemplary manners in which thecompositions, methods and/or devices disclosed herein may beincorporated into personal protection devices. Firstly, FIG. 1schematically shows a view in cross-section of an exemplary filtersystem 30. Filter system 30 includes interior space 31 that cart befilled with filter media 33 containing an adduct as described herein(filter media 33 can, for example, comprise activated carbon particles,granules, etc., that comprise TEDA/polycarboxylic acid adduct, asdescribed previously herein).

Interior 31 optionally may further include one or more additional filtermedia 35. For example, additional filter media 35 can include a COoxidation catalyst in the form of catalytically active gold depositedonto titania guest particles and further supported upon carbonaceoushost particles, as described in US Patent Publication 2007/027079. Ashas been described in detail herein, such a configuration is madepossible by the fact that the TEDA/polycarboxylic acid adduct on filtermedia 33 can co-exist in the same filter system with filter media 35containing the CO oxidation catalyst without undue poisoning of the COoxidation catalyst.

Filter media 33 and optional filter media 35 are shown as beingintermingled in the same filter bed in interior 31 in the exemplaryembodiment pictured in FIG. 1. A wide variety of other deploymentstrategies also may be used. As one alternative, filter media 33 andfilter media 35 may be provided in separate filter beds within interior31 so that the incoming air passes first through one of the beds andthen the other. Either filter media 33 comprising the adduct, or filtermedia 35 comprising a catalyst, can be placed upstream, according to thediscussions previously presented herein.

The relative amounts of the filter media 33 and filter media 35 used ininterior 31 may vary over a wide range. By way of example, the weightratio of filter media 33 to filter media 35 may be at least about 1:50,at least about 1:20, or at least about 1:5. In additional embodiments,the weight ratio of filter media 33 to filter media 35 may be at mostabout 50:1, at most about 20:1, or at most about 5:1.

Referring still to exemplary filter system 30 of FIG. 1, housing 32 andperforated cover 34 surround filter media 33 and filter media 35. In useof the system, air (or any gaseous stream to be filtered) enters throughopenings 36 and comes into contact with filter media 33 and filter media35, whereupon at least some portion of potentially hazardous substances(if present in the air) are absorbed, caused to react, or otherwisetreated or removed from the air, by filter media 33 and filter media35). The air then exits via valve 38 mounted on support 40.

Spigot 42 and bayonet flange 44 enable filter system 30 to bereplaceably attached to a respiratory protection device such as theillustrative exemplary respiratory device 50 shown in FIG. 2. Device 50is a so-called half mask similar those described in U.S. Pat. No.5,062,421 and US Patent Publication 2006/0096911. Device 50 includes asoft, compliant face piece 52 that can be insert-molded around arelatively thin, rigid structural member or insert 54, Insert 54includes exhalation valve 55 and recessed, bayonet-threaded openings(not shown) for removably attaching elements 30 in the cheek regions ofdevice 50. Adjustable headband 56 and neck straps 58 permit device 50 tobe securely worn over the nose and mouth of the wearer.

FIG. 3 schematically shows a view in cross-section of another exemplaryfilter system 130. Filter system 130 includes housing 132 defininginterior space 131 that contains filter media 133 containing an adductas described herein (interior space 131 can optionally also containadditional filter media, as described above). Filter system 130 furthercomprises porous polymeric filtration layer 137 that is positionedupstream of filter media 133. In the particular configurationexemplified in FIG. 3, the porous polymeric filtration layer 137 ispositioned outward of perforated divider 134. Such a configuration canbe achieved, for example, by supplying layer 137 in a cap 139 (whichcomprises openings 141 to allow air flow) which can be snapped orotherwise fastened or attached to filter system 130. Such an exemplaryconfiguration is shown in FIG. 3.

In use of the system, ambient air enters filter system 130 throughopenings 141 and passes through porous polymeric filtration layer 137,whereupon at least some portion of particles (if present in the air) areremoved from the air. The air then passes through openings 136 and comesin contact with filter media 133, whereupon at least some portion ofpotentially hazardous substances (if present in the air are absorbed,caused to react, or otherwise treated or removed from the air, by filtermedia 133. The air then exits via valve 138 mounted on support 140.

The filter system of FIG. 3 can be incorporated into a personalrespiratory protection device similar to that of FIG. 2, in similarmanner as described earlier.

EXAMPLES

The disclosures found herein will be further described with regard tothe following detailed examples. These examples are offered to furtherillustrate the various specific and preferred embodiments andtechniques. It should be understood, however, that many variations andmodifications may be made while remaining within the scope of thepresent invention.

Adduct Compositions and Properties

In the following examples, chemical reagents were obtained fromSigma-Aldrich, St. Louis, Mo., unless otherwise stated.

Characterization by X-Ray Diffraction Analysis was performed usingmethods and apparatus well known to those of skill in the art.Specifically, XRD was performed by collecting reflection geometry datain the form of a (θ/2θ) survey scan by use of a Philips (PANalytical,Westborough, Mass.) vertical diffractometer, copper K_(α) radiation, andproportional detector registry of the scattered radiation. Thediffractometer was fitted with variable incident beam slits, fixeddiffracted beam slits, and a graphite diffracted beam monochromator. Thesample was mulled in an agate mortar and applied as a dry powder to azero background specimen holder composed of single crystal quartz. Thesurvey scan was conducted from 3 to 55 degrees (2θ) using a 0.04-degreestep size and 6-second dwell time. X-ray generator settings of 45 kV and35 mA were employed. Analysis of resulting powder diffraction data wasaccomplished by use of Jade (version 7.5, Materials Data Inc.,Livermore, Calif.) diffraction software suite. All two-theta peaks wereconverted to unit cell interplanar spacings in Angstroms as calculatedaccording to Braggs law, and are reported as such. In all cases, theinterplanar spacing corresponding to the peak of highest intensity isreported as the (100) datum, with all other spacings normalized to that.For example, an interplanar spacing peak at 4.5 Å that had 14% relativeintensity compared to the 100% peak would be reported as 4.5 (14).

Characterization by Infrared (IR) Spectrometry was carried out by use ofstandard methods and apparatus well known to those of skill in the art.Spectra were determined on Nujol mulls; only characteristic bands arereported. Nuclear Magnetic Resonance (NMR) Spectroscopy was likewisecarried out by use of standard methods and apparatus well known to thoseof skill in the art. Differential Scanning calorimetric (DSC) analysisand Thermogravimetric Analysis (TGA) were performed according to methodswell known to those of skill in the art, using TA Instruments MDSC 2920and TGA 2950, respectively. The DSC instrument was calibrated usingindium and tin standards. The temperature calibration on the TGAinstrument was performed using nickel and alumel standards. A nominalheating rate of 10° C./minute was used for DSC analysis and a heatingrate of 50° C./minute was used for TGA analysis. Nitrogen purge at 50mL/minute was applied for both DSC and TGA.

Uncertainties (e.g., plus or minus values) are not reported individuallyfor the various numerical values, parameters and results in the examplesbelow. However, all such numbers will be understood by those of skill inthe art of XRD, IR, NMR, DSC, TGA, etc., as having the precisioncorresponding to typical analyses performed using such methods. That is,sonic variation in these values will be expected, depending on samplepreparation and experimental technique, and on the precision of themeasuring equipment used.

Example 1 TEDA-Succinic Acid

A solution of TEDA (11.8 g, 0.1 mole) in 50 mL water was prepared. 5.9 g(0.05 mole) succinic acid was stirred into 50 mL water, which provided ahazy appearing suspension or solution. The TEDA solution and thesuccinic acid solution were combined and stirred, at which point aclear, colorless solution was obtained. Water was removed at 50° C.under reduced pressure during which process a solid product precipitatedfrom solution. The solid was kept under dynamic vacuum for 16 hrs, afterwhich the final solid product weighed 11.2 g.

Elemental analysis revealed the following elements to be present at theweight percentages reported below. Also presented (in parentheses) arethe calculated weight percentages that correspond to a chemical formulaof C₁₀H₁₈N₂O₄, which would represent a 1:1 stoichiometric ratio of TEDA(C₆H₁₂N₂) and succinic acid (C₄H₆O₄).

(Experimentally-Found Versus 1:1 Stoichiometric Ratio-Calculated WeightPercentages are Reported Similarly in Succeeding Examples.)

Carbon: 51.2 Wt. % (52.2); Hydrogen 7.5 (7.8); Nitrogen 11.6 (12.2),

X-ray diffraction revealed at least the following peaks: 4.4 (100), 2.4(14), 3.1 (12), 4.1 Å (11).

Infrared analysis revealed at least the following peak: 1693 cm⁻¹

Differential scanning calorimetry analysis revealed melting endothermsat 59° C. and 53° C.

Example 2. TEDA-Succinic Acid-H₂O

Succinic acid (5.9 g, 0.05 mole) and TEDA (5.6 g, 0.05 mole) weredissolved in 500 mL ethanol at 60° C. The clear solution was placed in abeaker and left to evaporate. After 3 days, only about 50 mL solventremained. Filtration yielded 9.4 g (81%) white crystals that were washedtwice with 5 mL of cold ethanol then air dried. After cooling o 4° C.,the combined filtrate and washings deposited 1.3 g additional product.

Elemental analysis (experimentally found versus calculated forC₁₀H₂₀N₂O₅):

Carbon 48.3 (48.4); Hydrogen 7.7 (8.1); Nitrogen 9.8 (11.3),

X-ray diffraction revealed at least the following peaks: 3.9 (100), 5.0(89), 4.3 (62), 5.6 (55), 3.8 Å (51).

Infrared analysis revealed at east the following peaks: 3561, 3476, 2480(broad), 1690, 1642 cm⁻¹.

Thermal Gravimetric Analysis (TGA) revealed about a 6% weight loss by126° C. This appeared to represent loss of approximately one water ofhydration per adduct (the calculated weight loss which would be expectedbased on 1:1 TEDA/succinic acid adduct losing one water of hydrationwould be 7.3 wt. %).

Example 3 TEDA-Tartaric Acid

TEDA (11.2 g, 0.1 mole) and tartaric acid (L-(+)-tartaric acid, 15.0 g,0.1 mole, Merck Co., Rahway, N.J.) were combined with stirring in 50 mLwarm water. Water was removed at 60° C. using a rotary evaporator. Theresidue was kept under dynamic vacuum at 60° C. for 24 hrs. Thereremained 25.6 g (98%) of product as white chunks.

Elemental analysis (experimentally found versus calculated forC₁₀H₁₈N₂O₆):

Carbon 45.9 (45.8); Hydrogen 7.0 (6.9); Nitrogen 10.8 (10.7).

X-ray diffraction revealed at least the following peaks: 4.9 (16), 4.5(100), 2.4 Å (16).

Infrared analysis revealed at least the following peaks: 3423, 3340,1649 cm⁻¹

Differential scanning calorimetry analysis revealed a melting endothermat 66° C. (without recrystallization).

¹⁵N nuclear magnetic resonance (NMR) of the solid product revealed atleast a peak at δ30 (ppm, with respect to liquid NH₃).

Example 4 TEDA-Malanic Acid

Malonic acid (10.4 g, 0.1 mole) was added to a solution of 11.2 g (0.1mole) TEDA in 50 mL ethanol. After stirring for 1 hr, the mixture washeated to boiling then cooled to room temperature. Filtration afforded9.4 g (44%) product as white crystals.

Elemental analysis (experimentally found versus calculated forC₉H₁₆N₂O₄):

Carbon 49.9 (50.0); Hydrogen 7.1 (7.4); Nitrogen 12.7 (13.0).

X-ray diffraction revealed at least the following peaks: 6.2 (31), 5.5(44), 4.8 (36), 4.6 (57), 3.9 (85), 3.6 (100), 2.5 Å (35).

Infrared analysis revealed at least the following peaks: 2350, 1702 cm⁻¹

Differential scanning calorimetry analysis revealed no observablemelting endotherm.

Example 5 TEDA-Citric Acid

Anhydrous citric acid (19.2 g, 0.1 mole, Biorad Corp., Richmond, Calif.)was added to a solution of TEDA (11.2 g, 0.1 mole) in 75 mL ethanol. Themixture was heated to boiling, cooled to room temperature then stirredfor 14 hrs. Filtration afforded the product as white crystals, 29.0 g(96%) after vacuum drying.

Elemental analysis (experimentally found versus calculated forC₁₂H₂₀N₂O₇):

Carbon 46.5 (47.4); Hydrogen 6.5 (6.6); Nitrogen 9.1 (9.2).

X-ray diffraction revealed at least the following peaks: 5.0 (44), 4.9(81), 4.9 (39), 4.7 (100), 4.0 Å (28).

Infrared analysis revealed at least the following peaks: 3408, 2470,1958, 1730 cm⁻¹.

Example 6 TEDA-Malic Acid

dl-Malic acid (13.4 g, 0.1 mole, Sigma Chemical Co., St. Louis, Mo.) wasdissolved in 100 mL warm ethanol. With vigorous stirring, 11.2 g (0.1mole) TEDA in 25 mL ethanol was added. The product separated as a thickwhite precipitate. It was isolated by filtration, sucked dry then driedunder vacuum. The yield was 22.6 g (92%).

Elemental analysis (experimentally found versus calculated forC₁₀H₈N₂O₅):

Carbon 49.1 (48.8); Hydrogen 7.2 (7.3); Nitrogen 11.3 (11.4).

X-ray diffraction revealed at least the following peaks: 6.2 (31), 5.5(44), 4.8 (36), 4.6 (57), 3.9 (55), 3.4 Å (100).

Infrared analysis revealed at least the following peaks: 3433, 2457,1885, 1717 cm⁻¹.

Example 7 TEDA-Glutamic Acid

TEDA (11.2 g, 0.1 mole) was added to a suspension of 14.7 g (0.1 mole)1-glutamic acid in 150 mL hot water. The resulting clear solution wastaken to dryness on a rotary evaporator. The product was pulverized in amortar then vacuum dried for 16 hrs at 60° C. The yield was 24.7 g(95%).

Elemental analysis (experimentally found versus calculated forC₁₁H₂₁N₃O₄):

Carbon 51.2 (51.0); Hydrogen 7.9 (8.1); Nitrogen 15.7 (16.2).

Infrared analysis revealed at least the following peaks: 3048, 2573,2522, 2135, 1638, 1592 cm⁻¹.

Thermal Gravimetric Analysis showed a sharp (weight loss rate) peak at170° C. (representing about 35% weight loss) followed by broad peaks at220, 224 and 295° C. Substantial (6%) residue remained at 988° C.possibly indicative of gross decomposition of the sample rather thanvolatilization.

Thermogravimetric Testing Summary

Thermogravimetric test data for the adducts of Examples 1-7 (Example 2excepting) are presented in Table 1. In these data, T_(max) (adduct) isthe measured T_(max) (temperature of maximum rate of weight loss) of theadduct; T_(max) (acid) is the measured T_(max) of the carboxylic acidalone.

TABLE 1 T_(max) Data for Adducts and Parent Polycarboxylic Acids ExampleCarboxylic Acid T_(max) (adduct) (° C.) T_(max) (acid) (° C.) 1 Succinic144 182 3 Tartaric 206 211 4 Malonic 173 155 5 Citric 182 192 6 Malic216 196 7 Glutamic 170 215

Cycologen Chloride Service Life Tess

A test system is used to subject various sorbent samples to cyanogenchloride challenges in order to assess their performance for removingcyanogen chloride from gaseous streams. High-pressure compressed air isreduced in pressure, regulated, and filtered by a regulator (3M ModelW-2806 Air Filtration and Regulation Panel, 3M, St. Paul, Minn.) toremove particulates and oils. A valve (Hoke Inc., Spartanburg, S.C.) isused to set the desired main airflow rate as measured by a flow meter(Dwyer Instruments, Michigan City, Ind.) with a range of 0 to 200 SCFH.The flow meter is calibrated using a dry gas test meter (American Meter,model DTM-325).

The main airflow passes through the headspace above a heated distilledwater bath and then into a 250 ml mixing flask. Relative humidity in themixing flask is monitored using a RH sensor (Type 850-252, GeneralEastern, Wilmington, Mass.). The RH sensor provides an electrical signalto a humidity controller (a PID controller series CN1201AT from OmegaEngineering, Stamford, Conn.) that delivers power to a submerged heaterto maintain the RH at the set point. Unless otherwise indicated, therelative humidity is controlled at 92%.

High purity cyanogen chloride is prepared using the method described byH. Schroder in Z. anor. allg. Chem. 297, 296 (1958) and stored in asteel lecture bottle.

K₂[Zn(CN)₄]+4Cl₂→4ClCN+2KCl+ZnCl₂

Sodium pyrophosphate at 5% of the cyanogen chloride weight is added as astabilizer. The lecture bottle of cyanogen chloride provides a flow ofcyanogen chloride vapor.

An Aalborg 150 mm PTFE-glass rotameter with flowtube 042-15-GL is usedto measure cyanogen chloride volumetric flow. A stainless steel, finemetering valve (Whitey Co. SS21RS4, Highland Heights, Ohio) is used toset the desired cyanogen chloride flow rate.

The combined cyanogen chloride/air mixture at a concentration of 550 ppmcyanogen chloride and 92% RH flows at a flowrate at 32 L/min into apolycarbonate box equipped with 29/42 connections at the top and bottom.The test fixture containing the sorbent to be tested is mounted onto thebottom 29/42 fitting. (A drawing of a suitable fixture is shown in FIG.2 of ASTM Standard Guide for Gas-Phase Adsorption Testing of ActivatedCarbon—D5160-95). A specified sorbent volume, typically 75 mL, is loadedinto the 3.5 inch inner diameter aluminum test fixture. The fixture isloaded with sorbent using a snowstorm filling technique in which thesorbent falls into the test fixture through a loading column containingscreens to evenly distribute the sorbent across the bed. Typical beddepth is approximately 1.2 cm (0.45 in),

To start the test, a steady 32 L/min flow of a cyanogen chloride/airmixture at 550 ppm and 92% RH is introduced into the polycarbonate boxthrough the top 29/42 connection. Cyanogen chloride concentrationexiting the sorbent bed is measured with a SRI 8610C gas chromatograph(SRI Instruments, Torrance, Calif.) equipped with a gas sampling valveand a hydrogen flame ionization detector A vacuum source continuouslydraws approximately 50 mL/min of sample from the test outlet through thegas sampling valve of the GC. Periodically the valve injects a sampleonto a 6 ft×⅛ inch column of 10% Carbowax 20M on Chromosorb W-HP 80/100(Alltech part 12106PC, Alltech Associates, Deerfield, Ill.). Cyanogenchloride is separated from air and its concentration measured by ahydrogen flame ionization detector (minimum detectable cyanogen chlorideconcentration about 0.5 ppm). The GC is calibrated using cyanogenchloride in air mixtures prepared by injecting known volumes of cyanogenchloride vapor into a 39.2 L stainless steel tank filled with air. Aninternal fan circulates the mixture inside the tank. The vacuum sourcedraws a sample of the mixture into the gas sampling valve of the GC foranalysis. Calibration of the FID is typically linear over the entirerange from 0.5 to 600 ppm cyanogen chloride.

A plot of ppm cyanogen chloride vs. time is generated and used todetermine the Cyanogen Chloride Service Life (also known as the CKService Life or CK Lifetime). In this test, the Cyanogen ChlorideService Life is defined as the time (from initial cyanogen chlorideexposure) at which greater than 3 ppm cyanogen chloride is detected onthe downstream side of the filter. This Service Life is recorded and canbe used to compare the relative performance of the various samples.

Gold Catalyst Test

Catalyst poisoning tests are performed to determine the effect ofvarious materials (e.g., TEDA/polycarboxylic acid adduct samples) ongold CO oxidation catalysts. In all cases, the gold catalyst that isused is prepared in similar manner to that described in US PatentPublication 2007/0207079, Example 3.

20 ml of sample (e.g., activated carbon containing various adducts,etc.) are poured into an 8 oz glass jar. A 20 ml vial containing 7 ml ofthe above-references gold catalyst is also placed, uncapped, within the8 oz jar. The 8 oz jar is then capped and placed in a 71° C. oven for 7days. After removal from the oven and cooling to room temperature, the 8oz jar is opened, and the 20 ml vial containing the gold catalyst isremoved and capped until catalyst performance testing is conducted.

Catalyst performance testing is conducted in similar manner to theprocedure described in US Patent Publication 2005/0095189, Test Method#2. The catalyst is exposed to a gaseous stream with a carbon monoxide(CO) concentration of 3600 ppm and a flow rate of 9.61 pm. The carbonmonoxide concentration downstream from the catalyst is detected and atable of ppm (part per million) CO vs. time is generated, (in a slightdifference from the test method of US Patent Publication 2005/0095189),the ppm of CO at a time of 23 minutes (from the initial CO exposure) isreported, and can be used to compare the relative performance ofcatalysts that have been exposed to various samples.

Comparative Example C1

A sample of gold catalyst was prepared in similar manner to that listedin US Patent Publication 2007/0207079, Example 3, and was aged accordingto the procedure outlined in the Gold Catalyst CO Value Test above, butwithout any exposure to TEDA or adduct.

The sample was found to exhibit a Gold Catalyst Test value 128 ppm CO(measured at 23 minutes per the above procedure), as shown in Table 2.

Comparative Example C2

TEDA was coated on 12×20 Kuraray GG activated carbon (Kuraray ChemicalCompany, Osaka JP) by incipient wetness coating, in similar manner tothat outlined in the following procedure: an aqueous mixture wasprovided that contained approximately 3% TEDA based on the carbon mass.Small incremental amounts of the mixture were added to approximately 50g of GG carbon, until the incipient wetness point appeared to have beenreached (by visual inspection). With the water to carbon ratio thatcorresponded to an incipient wetness condition thus determined, aselected amount of aqueous mixture was prepared, at a selected TEDAconcentration, such that when the aqueous TEDA mixture was added tocarbon at the incipient wetness ratio, a nominal TEDA loading on thecarbon of 3 parts per hundred would result. The aqueous TEDA mixture wasthen added in small incremental amounts, with frequent stirring, to abatch of activated carbon until the targeted incipient wetness ratio wasreached. The carbon was then allowed to soak for two hours withoccasional mixing. The carbon was then spread in a single layer in aglass baking dish and dried for two hours at 105° C.

This sample was found to have a Cyanogen Chloride Service Life of 14minutes and a Gold Catalyst Test value of 2216 ppm CO, as shown in Table2.

Comparative Example C3

An activated carbon was prepared in similar manner to the methodsdescribed in U.S. Pat. No. 5,344,626, Example Six. The incipient wetnessratio was determined, and thereafter an aqueous mixture of TEDA wasprepared and deposited onto the activated carbon by incipient wetnesscoating, in similar manner as that described above in ComparativeExample 2.

A sample of this activated carbon with TEDA deposited thereon, whendried for two hours at 105° C. was found to have a Cyanogen ChlorideService Life of 18 minutes and a Gold Catalyst Test value of 3117 ppmCO. A sample when dried for six hours at 105° C. was found to have aCyanogen Chloride Service Life of 29 minutes and a Gold Catalyst Testvalue of 1049 ppm CO.

Examples 8-11 TEDA/Polycarboxylic Acid Adducts on the Activated Carbonof Comparative Example C2

For Kuraray GG activated carbon, the weight ratio of water thatcorresponds to the incipient wetness point was determined Aqueousmixtures of TEDA and a polycarboxylic acid were made by weighing andstirring the materials into water in amounts shown in Table 1 (in the“Mass Water”, “Mass TEDA”, and “Mass Acid” columns). The amount of TEDAadded to each aqueous mixture was chosen so as to combine with theamount of mixture to result in a final deposited amount of TEDA of about3 parts by weight TEDA per hundred parts of carbon. (For each sample,the specific calculated Final Weight of TEDA deposited on the carbon, ispresented in the “Final Wt. %” column of Table 2). The amount ofpolycarboxylic acid added to each aqueous mixture was chosen to as toprovide a nominal 1:1 stoichiometric ratio of polycarboxylic acid toTEDA.

Each aqueous mixture was introduced into/onto the amount of GG carbon(12×20 size) listed in Table 2 (“Mass GG”) via the incipient wetnesstechnique, using the aqueous mixture/activated carbon weight ratio(determined as discussed above) for that that particular sample. Thesamples were dried for two hours at 105° C. The activated carbon withthe TEDA/polycarboxylic acid adduct deposited thereupon, was then testedin the Cyanogen Chloride Service Life test and the Gold Catalyst Test,with the results shown in Table 3.

TABLE 2 TEDA/Polycarboxylic Acid Adduct on GG Carbon - Composition MassMass Mass GG Water TEDA Mass Final Wt. Example Acid (g) (g) (g) Acid (g)% TEDA 8 Succinic 250.56 216.36 6.99 7.38 2.8 9 Citric 125.73 108.183.61 6.08 2.9 10 Malonic 126 109.09 3.46 3.42 2.8 11 Glutamic 125.97108.81 3.49 4.56 2.8

TABLE 3 TEDA/Polycarboxylic Acid Adduct on GG Carbon - Performance GoldCatalyst CK Service Test (ppm Example Adduct Life (min) CO @ 23 min)Comparative-1 None (gold catalyst only) — 128 Comparative-2 None (TEDAonly) 14 2216  8 TEDA/Succinic 25 105  9 TEDA/Citric 27 1104 10TEDA/Malonic 15 410 11 TEDA/Glutamic 20 3093

Examples 12-15 TEDA/Polycarboxylic Acid Adduct on the Activated Carbonof Comparative Example C3

Activated carbon was prepared in similar manner to the methods describedin U.S. Pat. No. 5,344,626, Example Six. The weight ratio of water thatcorresponded to the incipient wetness point was determined. Aqueousmixtures of TEDA and a polycarboxylic acid were made, deposited onto thecarbon, and dried, in similar manner as described above for Examples8-11. Again the TEDA amount was targeted to correspond to a final ratioof about 3 parts TEDA per 100 parts carbon, with the amount ofpolycarboxylic acid chosen so as to provide a nominal 1:1 stoichiometricratio of polycarboxylic acid to TEDA. The activated carbon with theTEDA/polycarboxylic acid adduct deposited thereupon, was then tested inthe Cyanogen Chloride Service Life test and the Gold Catalyst Test, withthe results shown in Table 5.

TABLE 4 TEDA/Polycarboxylic Acid Adduct on the Activated Carbon of U.S.Pat. No. 5,344,626, Ex. 6 - Composition. Mass Mass Mass GG Water TEDAMass Final Wt. Example Acid (g) (g) (g) Acid (g) % TEDA 12 Malonic250.53 206.24 6.63 6.09 2.6 13 Succinic 126.18 91.85 3.07 5.16 2.4 14Citric 125.82 94.12 2.99 2.95 2.4 15 Glutamic 125.45 93.91 3.01 3.93 2.4

TABLE 5 TEDA/Polycarboxylic Acid Adduct on the Activated Carbon of U.S.Pat. No. 5,344,626, Ex. 6 - Performance. Gold Catalyst CK Service Test(ppm Example Adduct Life (min) CO @ 23 min) Comparative-1 None (goldcatalyst — 128 only) Comparative-3 None (TEDA only) 18 3117 (dried 2hours) 29 1049 (dried 6 hours) 12 TEDA/Malonic 48 200 13 TEDA/Succinic75 167 14 TEDA/Citric 52 150 15 TEDA/Glutamic 38 119

Example 16 TEDA/Poly(Acrylic Acid) on the Activated Carbon ofComparative Example C3

Activated carbon was prepared in similar manner to the methods describedin U.S. Pat. No. 5,344,626, Example Six. In a 500 mL beaker withmagnetic stirring, 12.59 grams of a 35 wt. % aqueous solution ofpoly(acrylic acid) of average M_(w)=250,000, was combined with 214.12grams DI water. 6.90 grams of TEDA was added slowly and stirred untildissolved. 199.86 grams of the solution was poured over 250.53 grams ofthe activated carbon in a 1 L beaker, stirred slightly, and allowed tosit for 16 hrs. The activated carbon was then dried for two hours at105° C. The activated carbon with TEDA/poly(acrylic acid) depositedthereupon, was then tested in the Cyanogen Chloride Service Life testand the Gold Catalyst Test, with the results shown below in Table 7.

TABLE 6 TEDA/Poly(acrylic acid) on the Activated Carbon of U.S. Pat. No.5,344,626, Ex. 6 - Composition. Mass Mass Mass Mass Water TEDA AcidFinal Wt. Example Acid GG (g) (g) (g) (g) % TEDA 16 Poly(acrylic) 250.53214.12 6.90 4.41 2.8

TABLE 7 TEDA/Poly(acrylic acid) Adduct on the Activated Carbon of U.S.Pat. No. 5,344,626, Ex. 6 - Performance. Gold Catalyst CK Service Test(ppm Example Adduct Life (min) CO @ 23 min) Comparative-1 None (Goldcatalyst — 128 only) Comparative-3 None (TEDA only) 18 3117 (dried 2hours) 29 1049 (dried 6 hours) 16 TEDA/Poly(acrylic 15 163 acid)

Porous Polymeric Electret Webs

Porous polymeric nonwoven webs were prepared by melt-blowing methodssimilar to those described in Wente, Van A., “Superfine ThermoplasticFiber”, Industrial and Engineering Chemistry, vol. 48. No. 8, 1956, pp1342-1346. The webs were fluorinated by plasma treatment in anatmosphere containing C₃F₈, using methods similar to those described inUS Patent Publication 2003/0134515. The webs were charged by impingingwater on the web, using methods similar to those described in US PatentPublication 2003/0134515.

Electret Aging Tests Porous polymeric electret web tests are performedto determine the effect of various materials (e.g., TEDA/polycarboxylicacid adduct samples) on the filtration properties of electret webs. 75ml of sample (e.g., activated carbon containing various adducts, etc.)are poured into a 32 ounce glass jar. The jar is swirled to create auniform layer. Four 5.25″ (13.2 cm) discs of porous polymeric web areplaced vertically against the walls of the jar. The 32 ounce jar is thencapped and placed in a 71° C. oven for 7 days. After removal from theoven and cooling to room temperature, the jar is opened, and the testwebs are removed and placed in a sealed jar until performance testing isconducted.

Dioctyl Phthalate Penetration Test

A dioctyl phthalate (DOP) aerosol challenge penetration test isperformed using a Certitest Model 8130 Automated filter Test (availablefrom TSI, Inc. of Shoreview, Minn.), using equipment and proceduressimilar to those described in the NIOSH Determination of ParticulateFilter Penetration to Test Against Liquid Particulates for NegativePressure Air Purifying Respirators Standard Test Procedure No.RCT-APR-0051, as set forth in 42CFR, Part 84, Subpart G, Section84.63(a)(c)(d) and Subpart K, Section 84.181; Volume 60, No. 110, Jun. 81995. The DOP particles are generated at a nominal geometric meandiameter of approximately 185 nm. The particles are impinged on a sampleof porous polymeric electret web (approximately 100 cm² exposed samplearea) in an gaseous stream moving at a flow rate of approximately 42.5liters per minute, for a period of approximately 25 seconds. No ionizeror aerosol neutralizer is operated during the test. The DOP %Penetration for a given sample is calculated based on the measured DOPconcentrations in the gaseous stream upstream and downstream from theweb sample (as measured by light scattering). Penetration is reported in%.

Comparative Example C4

A sample of porous polymeric electret web was prepared as describedabove, and was not exposed to 71° C. aging. The sample was found toexhibit a DOP penetration of 8.3%, as shown in Table 8.

Comparative Example C5

A sample of porous polymeric electret web was prepared as describedabove, and was aged at 71° C. according to the procedure outlined in theElectret Aging Test but without any TEDA or adduct being present. Thesample was found to exhibit a DOP penetration of 18.1%, as shown inTable 8.

Comparative Example C6

An activated carbon was prepared in similar manner to the methodsdescribed in U.S. Pat. No. 5,344,626, Example Six. An aqueous mixture ofTEDA was prepared and deposited onto the activated carbon by incipientwetness coating in similar manner as that described above in ComparativeExample 3. In this example, the TEDA concentration in the aqueousmixture, and the amount of aqueous mixture, were chosen to as to providea nominal loading of TEDA on the activated carbon of 1.5%. The sample ofthis activated carbon with TEDA deposited thereon was dried for 6 hoursat 105° C.

A sample of porous polymeric electret web was prepared as describedabove, and was aged at 71° C. In the presence of the TEDA-loadedactivated carbon according to the procedure outlined in the ElectretAging Test. The sample was found to exhibit a DOP penetration of 54.1%,as shown in Table 8.

Examples 17-19 Electret Webs Exposed to TEDA/Polycarboxylic Acid Adducton the Activated Carbon of Comparative Example C2 or C3

Kuraray GG activated carbon was obtained; and, activated carbon wasprepared in similar manner to the methods described in U.S. Pat. No.5,344,626, Example Six. The weight ratio of water that corresponded tothe incipient wetness point was determined as outlined above forComparative Examples 2 and 3 respectively. Aqueous mixtures of TEDA anda polycarboxylic acid were matte, deposited onto the carbon, and dried,in similar manner as described above. The TEDA concentration and theamount of aqueous TEDA mixture were chosen in various cases so as tocombine to achieve a nominal TEDA loading on the activated carbon ofeither 1.5% or 3.0%, as noted below. The amount of polycarboxylic acidadded to each aqueous TEDA mixture was chosen so as to provide a nominal1:1 stoichiometric ratio of polycarboxylic acid to TEDA. Porouspolymeric electret web samples were then subjected to 71° C. aging inthe presence of the activated carbon bearing the adduct (with exceptionsin the comparative examples as noted). The webs were then tested in theDioctyl Phthalate Penetration Test, with the results as shown in Table8.

TABLE 8 Electret Webs Exposed to TEDA/Polycarboxylic Acid Adducts onActivated Carbons - Performance. Web 71° C. DOP Aging TEDAPolycarboxylic Penetration Example Condition Loading Acid (%)Comparative-4 None None None 8.3 Comparative-5 Without TEDA None None18.1 Comparative-6 With TEDA 1.5% None 54.1 17 With Adduct 1.5% SuccinicAcid 21.2 18 With Adduct 3.0% Succinic Acid 23.0 19 With Adduct 3.0%Citric Acid 23.0

The tests and test results described above are intended solely to beillustrative, rather than predictive, and variations in the testingprocedure can be expected to yield different results. The foregoingdetailed description and examples have been given for clarity ofunderstanding only. No unnecessary limitations are to be understoodtherefrom. In particular, headings and/or subheadings in this disclosureare provided for convenience of reading, and no unnecessarilylimitations are to be understood therefrom.

The present invention has now been described with reference to severalembodiments thereof. It will be apparent to those skilled in the artthat changes can be made in the embodiments described without departingfrom the scope of the invention. Thus, the scope of the presentinvention should not be limited to the exact details and structuresdescribed herein, but rather by the structures described by the languageof the claims, and the equivalents of those structures.

1. A filter medium, comprising: a support; and, an adduct of triethylenediamine and a polycarboxylic acid provided on the support.
 2. The filter medium of claim 1 wherein the adduct is a 1:1 stoichiometric adduct.
 3. The filter medium of claim 1, wherein the support comprises an activated carbon that comprises a first metal salt wherein the metal is in group 6-12 of the periodic table, and a second metal salt that comprises a metal carbonate salt wherein the metal is in group 1 of the periodic table.
 4. The filter medium of claim 1, wherein the polycarboxylic acid contains at least one hydroxyl group that is not part of a carboxylic acid group.
 5. The filter medium of claim 1, wherein the adduct includes at least one water of hydration.
 6. The filter medium of claim 1, wherein the polycarboxylic acid is succinic acid.
 7. The filter medium of claim 1, wherein the support comprises a guest/host structure.
 8. The filter medium of claim 1, wherein the filter medium is in a respiratory protection device.
 9. A method of making a filter medium, comprising the steps of: providing triethylenediamine and at least one polycarboxylic acid; combining the triethylenediamine with the polycarboxylic acid under conditions effective to form an adduct thereof; and, causing the adduct to be provided on a support.
 10. The method of claim 9, wherein the method comprises mixing the triethylenediamine and the at least one polycarboxylic acid into a mixture, depositing the mixture onto the support, and drying the support.
 11. The method of claim 10, wherein the mixture comprises an aqueous solution or suspension that optionally comprises at least one alcohol.
 12. The method according to claim 10, wherein depositing the mixture on the support is performed by incipient wetness impregnation.
 13. A filter system, comprising: a filter medium comprising a support comprising an adduct of triethylenediamine and a polycarboxylic acid; and, a catalyst active for the oxidation of carbon monoxide.
 14. The filter system of claim 13, wherein the catalyst comprises gold clusters of size from about 0.5 nm to about 50 nm.
 15. The filter system of claim 13, wherein the filter system is in a respiratory protection device. 